The distinct stellar-to-halo mass relations of satellite and central galaxies: Insights from the IllustrisTNG simulations

Christoph Engler*, Annalisa Pillepich, Gandhali D. Joshi, Dylan Nelson, Anna Pasquali, Eva K. Grebel, Thorsten Lisker, Elad Zinger, Martina Donnari, Federico Marinacci, Mark Vogelsberger, Lars Hernquist

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


We study the stellar-to-halo mass relation (SHMR) for central and satellite galaxies with total dynamical masses above 1010.5 M⊙ using the suite of cosmological magnetohydrodynamical simulations IllustrisTNG. In particular, we quantify environmental effects on satellite populations from TNG50, TNG100, and TNG300 located within the virial radius of group- and clusterlike hosts with total masses of 1012-15.2 M⊙. At fixed stellar mass, the satellite SHMR exhibits a distinct shift towards lower dynamical mass compared to the SHMR of centrals. Conversely, at fixed dynamical mass, satellite galaxies appear to have larger stellar-to-total mass fractions than centrals by up to a factor of a few. The systematic deviation from the central SHMR is larger for satellites in more massive hosts, at smaller cluster-centric distances, with earlier infall times, and that inhabits higher local density environments; moreover, it is in place already at early times (z 2). Systematic environmental effects might contribute to the perceived galaxy-to-galaxy variation in the measured SHMR when galaxies cannot be separated into satellites and centrals. The SHMR of satellites exhibits a larger scatter than centrals (by up to ∼0.8 dex), over the whole range of dynamical mass. The shift of the satellite SHMR results mostly from tidal stripping of their dark matter, which affects satellites in an outside-in fashion: The departure of the satellite SHMR from the centrals' relation diminishes for measurements of dynamical mass in progressively smaller apertures. Finally, we provide a family of fitting functions for the SHMR predicted by IllustrisTNG.

Original languageAmerican English
Pages (from-to)3957-3975
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - 1 Jan 2021
Externally publishedYes

Bibliographical note

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  • Galaxies: Clusters: General
  • Galaxies: Evolution
  • Galaxies: Groups: General
  • Galaxies: Haloes


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